The calculated zero-temperature lattice parameters for the conventional 12-atom
unit cells are summarized in Table 2 and compared to the
experimental data [1]}, [2]}, [3]} (the cubic and
tetragonal experimental lattice parameters are extrapolated to zero temperature).
The energy differences between the three phases are also shown in the table.
AI calculations based on the PBEsol exchange-correlation functional [4]} describe very accurately the relaxed structures
compared to experiment, almost on par with benchmark many-electron
calculations [5]}. The MLFF results are in excellent agreement
with the AI ones, the differences being less than 0.2% for the lattice parameters
and less than 1 meV per atom for the energies. Note that here BLR and SVD perform
equally well.
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